Sun’s gravity could power interstellar video streaming

Need to send a message across interstellar space? Use the sun for a signal boost. A new proposal suggests that the sun’s gravity could be used to amplify signals from an interstellar space probe, allowing video to be streamed from as far away as Alpha Centauri. Better still, the technology to do it has already been invented.

Though we don’t have probes far out enough to take advantage of this technology yet, it may eventually come in handy for interstellar communications. Building the communications grid now makes calls to our own spacecraft – or that of another alien race – a future possibility.

To receive even a single-watt signal from a probe in Alpha Centauri, the nearest star system to our own, independent astrophysicist Michael Hippke found that an Earth-based instrument would need to be 53 kilometres across – bigger than New York City.

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In his study, Hippke proposes instead that a telescope about a metre across could relay the signal. It would just have to be placed at a point about 90 billion km from the sun – a distance that would optimise an effect known as gravitational lensing to magnify the signal.

The effect, predicted by Albert Einstein and first observed in 1919, bends and focuses light to a point as it passes the edge of a massive object such as the sun.

Talking to Alpha Centauri

Such a signal boost would be important for building receivers for any mission to interstellar space. Without it, we’d need to construct massive telescopes on Earth and send probes to interstellar space large enough to carry immense power sources.

With the gravitational-lensing effect, a little power would go a long way towards transmitting data back to our solar system. “Around the nearest stars, a handheld laser pointer could do it,” says Hippke. The data rate would be high enough that sending pictures and video is possible, although at present it would still take four years to receive any data stream from as far away as Alpha Centauri.

Off the shelf

Not so for Hippke’s design, which uses only off-the-shelf technologies. But that doesn’t mean it’s an easy feat. His proposed spacecraft must be more than four times as far away as the current position of Voyager 1, which is 20.8 billion km from the sun – the most distant spacecraft humans have sent into space to date, after being launched 40 years ago.

Any closer than 90 billion km and any signal boost would be lost because the sun would block it.

Slava Turyshev, a physicist at NASA’s Jet Propulsion Laboratory, said Hippke’s plan is “challenging but not impossible.” The receiving spacecraft needn’t even come to a complete stop because it could still get signals up to 300 billion km from the sun.

Turyshev says a slingshot around the sun might work to get one out to the 90-billion-kilometre mark in a time frame of 25 to 30 years.

Despite the challenges involved in such an ambitious project, Hippke says humans have launched larger space telescopes than what he is proposing. “This is much easier than building the Hubble Space Telescope,” he says.